WASHINGTON — We have a problem. The president proposes attacking Syria, and his top military officer cannot tell you the objective. Does the commander in chief know his own objective? Why, yes. "A shot across the bow," explained Barack Obama.

Now, a shot across the bow is a warning. Its purpose is to say: Cease and desist, or the next shot will sink you. But Obama has already told the world — and Bashar al-Assad in particular — that there will be no next shot. He has insisted time and again that the operation will be finite and highly limited. Take the shot, kill some fish, go home.

What then is the purpose? Dempsey hasn't a clue, but Secretary of State John Kerry says it will uphold and proclaim a norm and thus deter future use of chemical weapons. With a few Tomahawk missiles? Hitting sites that, thanks to the administration having leaked the target list, have already been scrubbed of important military assets?

This is risible. If anything, a pinprick from which Assad emerges unscathed would simply enhance his stature and vindicate his conduct.

Deterrence depends entirely on perception and the perception in the Middle East is universal: Obama wants no part of Syria.

Assad has to go, says Obama, and then lifts not a finger for two years. Obama lays down a red line, and then ignores it. Shamed finally by a massive poison gas attack, he sends Kerry to make an impassioned case for righteous and urgent retaliation — and the very next day, Obama undermines everything by declaring an indefinite timeout to seek congressional approval.

This stunning zigzag, following months of hesitation, ambivalence, contradiction and studied delay, left our regional allies shocked and our enemies gleeful. I had strongly advocated going to Congress. But it was inconceivable that, instead of recalling Congress to emergency session, Obama would simply place everything in suspension while Congress finished its Labor Day barbeques and he flew off to Stockholm and St. Petersburg. So much for the fierce urgency of enforcing an international taboo and speaking for the dead children of Damascus.

Here's how deterrence works in the Middle East. Syria, long committed to the destruction of Israel, has not engaged Israel militarily in 30 years. Why? Because it recognizes Israel as a serious adversary with serious policies.

In this year alone, Israel has four times launched airstrikes within Syria. No Syrian response. How did Israel get away with it? Israel had announced that it would not tolerate Assad acquiring or transferring to Hezbollah advanced weaponry. No grandiloquent speeches by the Israeli foreign minister. No leaked target lists. Indeed, the Israelis didn't acknowledge the strikes even after they had carried them out. Unlike the American president, they have no interest in basking in perceived toughness. They care only about effect. They care about just one audience — the party to be deterred, namely Assad and his allies.

Assad knows who did it. He didn't have to see the Israeli prime minister preening about it on world television.

And yet here is Obama, having yet done nothing but hesitate, threaten, retract and wander about the stage, claiming Wednesday in Sweden to be the conscience of the world, upholding not his own red line but the world's. And, incidentally, Congress' — a transparent attempt at offloading responsibility.

What should Congress do?

To his dovish base, Obama insists on how limited and militarily marginal the strike will be. To undecided hawks like Sens. John McCain and Lindsey Graham, who are prepared to support a policy that would really alter the course of the civil war, he vaguely promises the opposite — to degrade Assad's military while upgrading that of the resistance.

Problem is, Obama promised U.S. weaponry three months ago and not a rifle has arrived. This time around, what seems in the making is a mere pinprick, designed to be, one U.S. official told the Los Angeles Times, "just muscular enough not to get mocked."

That's why Dempsey is so glum. That's why U.S. allies are so stunned. There's no strategy, no purpose here other than helping Obama escape self-inflicted humiliation.

This is deeply unserious. Unless Obama can show the country that his don't-mock-me airstrike is, in fact, part of a serious strategy for altering the trajectory of the Syrian war, Congress should vote no.